I'm working on setting up a cmts lab a cisco ubr7246 and using isc dhcpd 4.1.1 on centos 6.x with some Arris TM602g cable modems and I'm having some trouble with the cable modems acknowledging their dhcp offer and then configuring.
The modems will get a dhcp discover to the dhcpd server and the dhcpd server will do a dhcp offer, but the modem doesn't seem to like the dhcp offer options.
The ubr7246 has the ip address 192.168.0.1 with ip addresses for the CM's and CPE's on a interface bundle with 10.0.0.1 for the CM's and 172.16.0.1 for the CPE's
My dhcpd server is at 192.168.0.10 and is running dhcpd and tftp for the CM configuration files.
My dhpcd.conf is below.
==================
authoritative;
ddns-update-style none;
shared-network "cmtslab" {
subnet 192.168.0.0 netmask 255.255.255.0 { } # dhcpd server subnet
# Subnet for customer personal equipment (CPE)
subnet 172.16.0.0 netmask 255.255.255.0 {
option routers 172.16.0.1;
option domain-name-servers 8.8.8.8, 8.8.4.4;
pool {
range 172.16.0.101 172.16.0.254;
allow unknown-clients;
default-lease-time 60;
max-lease-time 600;
} # End of the pool for CPE
} # End of the subnet for CPE
# Subnet for cable modems (CM)
subnet 10.0.0.0 netmask 255.255.255.0 {
option routers 10.0.0.1;
option domain-name-servers 8.8.8.8, 8.8.4.4;
option subnet-mask 255.255.255.0;
next-server 192.168.0.10;
option tftp-server-name "192.168.0.10";
default-lease-time 60;
max-lease-time 600;
option time-servers 10.0.0.1;
#UTC -6 hrs in seconds
option time-offset -21600;
option log-servers 192.168.0.10;
pool {
range 10.0.0.101 10.0.0.254;
#Default deny service boot file
filename "deny.bin";
#Default deny service boot file with alt. option for some cable modem's
option bootfile-name "deny.bin";
option domain-name "domain.net";
# Groups based on service level
group baseservice {
filename "baseservice.cm";
option bootfile-name "baseservice.bin";
}
#Sample Host #1 in shared subnet
host 111111111111 {
hardware ethernet 11:11:11:11:11:11;
option host-name "cm111111111111";
fixed-address 10.0.0.96;
group "baseservice";
}
host 222222222222 {
hardware ethernet 22:22:22:22:22:22;
option host-name "cm222222222222";
fixed-address 10.0.0.97;
group "baseservice";
}
} # End of the subnet pool for CM
} # End of the subnet for CM
} # End of dhcpd.conf
Routing problem?
Note that, DHCPDISCOVER and DHCPOFFER are broadcast,
but DHCPREQUEST and DHCPACK are unicast messages.
That ended up being the problem. We made some adjustments and we're all set with modems getting their configuration and coming online.
What Ips are being offered to the cable modems, you may be getting ips from the 172.xxx subnet even though you have fixed addresses specified. when you have a shared network it checks the subnets in order of the config file and chooses the first available ip. Since there is nothing restricting the cable modems from getting an ip from the 172. subnet they may be being offered ips from that subnet which do not have all the required options to boot a cable modem.
Thanks, at the time of testing, I just wanted to see the cable modems get an address. In further testing, I'll adjust the order of the config file or use some allow/deny statements to adjust where the cable modems/mta's/cpe go.